cr, dr and recent advances

Dr. Vishal SankpalNIMS, Hyderabad

Computed RadiographyDigital Radiography

Recent Advances

For nearly 100 years now, the photographic film has been used to record images

For over 60 years, intensifying screens have been used with x-ray films to obtain high quality images with lower radiation doses

Very recently it has become possible to record x-ray images without the use of conventional film-screen systems (CR and DR systems)

But even now, radiography using film-screen technology accounts for about 65 % of all diagnostic examinations

INTRODUCTION

Define the key terms used in digital imaging

List the equipment needed to perform digital imaging

Explain the computed radiography (CR) digital system

Explain the digital radiography (DR) system

Explain PACS and recent advances in digital radiography

Learning Objectives

Any Imaging Technique has following steps –

1. Image Acquisition2. Image Processing3. Image Display4. Image Storage

Radiography

Analog (Conventiona

l)Digital

Scanner (X-ray

digitizer)

Computed Radiography

(CR)

Direct Digital

Radiography (DR or DDR)

A conventional system uses an intensifying screen to create a latent image on x-ray film.

The film is then processed, creating a manifest image that can be interpreted by a physician.

It is later stored in the file room (physical storage for archival)

Conventional (Analog) Radiography

Method is film-based.

Method uses intensifying screens.

Film is placed between two screens.

Screens emit light when x-rays strike them.

Film is processed chemically.

Processed film is viewed on view-box (lightbox).

Chemical Processing in film radiography

10% of films are not available when we want them!15% of films are “hard” to locate or find!25% of films are “misplaced” or not retrievable

(misfiled).10% of films are lost (referrals, residents, etc.)Recent study – physicians spend two weeks/year

(100 hours/year) trying to locate or find the films they need.

Cost in physician time is estimated from $60 to $80 per study.

Problems with Film ?

Radiography

Analog Digital

Scanner (X-ray

digitizer)

Computed Radiograp

hy (CR)

Direct Digital Radiography (DR or DDR)

Definition –

Digital Imaging is any modality / method of imaging that creates an image that can be viewed or stored on a computer.

Digital imaging or Digitization ?

Concept began in the 1950s.

Early PACS systems were developed by the military to send images between Veterans Administration hospitals in the 1980s.

Early process involved scanning radiographs into the computer and sending them from computer to computer.

Images were then stored in PACS.

Computed and digital radiography followed.

Digital Radiography HISTORY

Digitization in Radiology -

CT (1970’s)FluoroscopyMRI (1980’s)Nuclear

MedicineMammographyUltrasound

X-Ray

Only recently, it has become technically possible and economically feasible to challenge film technique for projection radiography

Made possible by certain pre-requisite technological advances such as - high luminance and high resolution display

monitors high performance computers / workstations

Why so late ?

Radiography

Analog Digital

Scanner (X-ray

digitizer)

Computed Radiograp

hy (CR)


Scanner (X-ray digitizer)

A scanner is used to convert existing analog images into a digital format

Not cost-efficient

Hence, seldom used (old available films need to be converted into digital format)

Computed Radiography

Definition -

Computed Radiography (CR) is a process of capturing radiographic data from a Conventional X-ray machine and processing the data digitally to produce crisp and high quality radiographic images


Conventional X-ray machine / Tube

NIMS – SIEMENS Multiphos 15

Cassette with Imaging Plate

Light weigth aluminiumPlastic Steel frame

The front panel made up of low attenuation carbon fiber

Cassette structure

Approximately 1 mm thick

Imaging plate structure

Protective layerPhosphor layer

Anti-halo and reflecting layer

Base

Backing layer

Fluorinated Polymer Material – Protects the Phosphor layer

Protective layer



Base

Backing layer

Europium-activated Barium-fluorohalide (BaFX: Eu+2)

The phosphor crystals are usually cast into resin material to give them the form of plates

Phosphor layer



Base

Backing layer

To reduce scatter




Base

Backing layer

PET – Polyethylene Teraphtalate

Base



Base

Backing layer

Protects the base from damage

Backing layer



Base

Backing layer

The Imaging Plate looks like the intensifying screens found in Conventional film-screen cassettes

They are made of photostimulable phosphors

Instead of emitting light immediately when exposed to X-rays, the photostimulable phosphor has the special property of storing the X-ray energy in a latent form and releasing the same when stimulated by a laser energy in the CR Reader / Digitizer – photo Phosphorescence (c/w - fluorescence)

Imaging Plate (IP)

When phosphors are stimulated with X-ray photon energy, electron hole pairs are produced

In effect, Europium is excited to a higher energy level (excited state) leaving behind a hole / vacancy

Energy absorbed by the imaging plate must be transformed into electrical charges, which are then recorded and digitized.

Read out Process

The readout process should start immediately after exposure because the amount of stored energy decreases over time (latent image completely disappears by 24 hrs – spontaneous phosphorescence)

Stimulation with a scanning laser beam releases electrons

Falling back electrons emit luminescent light (phosphorescence)

Typical wavelength of the stimulating laser is 633 nm (usually helium-neon laser)

Typical wavelength of the emitted light is 390 nm(BLUE)

633 nm

390 nm

The emitted light intensity is proportional to the original incident X-ray intensity

The emitted light is captured with an optical array and a photomultiplier tube, the signals amplified and digitized (Analog to Digital converters - ADC)

The residual image is erased from the plate by an intense light source, which returns all electrons to their original state. This makes the plate ready to be reused for new exposures

How many times can we use a Storage Phosphor Plate?

• The life of a phosphor plate depends on how carefully it is handled. Physical damage to the plate will limit its useful life

• If properly cared for, a plate will produce thousands of images

• Imaging Plates are known to last more than 50000 Exposure Cycles !!!!!

1. Image Acquisition2. Image Processing3. Image Viewing / Display4. Image Storage

Rx

Network

Digitizer

Printing

Identification

Processing server

Exposure

Cassette with Imaging Plate

CR work flow

Radiography

Analog Digital

Scanner (X-ray

digitizer)

Computed Radiograp

hy (CR)


Direct Digital Radiography

INTRODUCTION

In CR, image acquisition is a two-stage process wherein image capture and image read out are done separately.

Direct digital radiography (DR) systems, on the other hand, use detectors that have a combined image capture and image read out capability.

Cassette-less system

DDR components -

A- vertical standB – TubeC – ConsoleD – Detector E - Couch

1. Image Acquisition2. Image Processing3. Image Display /

viewing4. Image Storage

Requires new installation (unlike CR)

There are different types of DR Systems available depending on the type of detectors used in them

(a) Flat panel detector (FPD) based systems

(b) Charge coupled device (CCD) array based system

Requires a photoconductor

Converts x-ray photons into electrical charges by setting electrons free.

Typical photoconductor materials include amorphous selenium, lead iodide, lead oxide, thallium bromide, and gadolinium compounds.

The most commonly used element is selenium.

Direct conversion

X-ray

Electrical signals

Directly

Selenium-based direct conversion DR systems are equipped with either a selenium drum or a flat-panel detector (FPD).

A rotating selenium-dotted drum, which has a positive electrical surface charge, is exposed to x-rays.

During exposure, a charge pattern proportional to that of the incident x-rays is generated on the drum surface and is recorded during rotation by an analog to- digital converter.

Selenium Drum

Amorphous selenium–based direct conversion DR systems.

1. A rotating selenium-dotted drum with a positive electrical surface charge is exposed to x-rays. 2. Alteration of the charge pattern of the drum surface is proportional to the incident x-rays. 3. The charge pattern is then converted into a digital image by an analog-to-digital (A/D) converter.

Selenium Drum…..

Several clinical studies have confirmed that selenium drum detectors provide good image quality that is superior to that provided by screen-film or CR systems. (ADVANTAGE)

However, because of their mechanical design, selenium drum detectors are dedicated thorax stand systems with no mobility at all. (DISADVANTAGE)

A newer generation of direct conversion DR systems make use of selenium-based flat-panel detectors.

These detectors make use of a layer of selenium with a corresponding underlying array of thin-film transistors (TFTs).

The principle of converting x-rays into electrical charges is similar to that with the selenium drum, except that the charge pattern is recorded by the TFT array, which accumulates and stores the energy of the electrons.

Flat-Panel Detectors (FPD)

A selenium-based flat-panel detector system

1. Incident x-ray energy is directly converted into electrical charges within the fixed photoconductor layer2. read out by a linked TFT array beneath the detective layer

Flat-Panel Detectors (FPD)…..Greater clinical usefulness, since the detectors can be mounted on thorax stands and Bucky tables (ADVANTAGE)

Another promising clinical application of selenium-based flat-panel detectors is in the field of Mammography (ADVANTAGE)

Studies indicate that the image quality provided by selenium-based flat-panel detectors is equivalent to that provided by other flat-panel detectors and selenium drum detectors (ADVANTAGE)

Indirect conversion

X-rays

Light

Electrical signals

Charged Coupled Device (CCD) is used

A CCD is a light-sensitive sensor for recording images that consists of an integrated circuit containing an array of linked or coupled capacitors.

X-ray energy is converted into light by a scintillator such as Thallium doped cesium iodide. The amount of light emitted is then recorded by the CCD, and the light is converted into electrical charges.

Indirect Conversion

CCD

Lens coupled Slot scan

An array consisting of several CCD chips forms a detector area similar to that of a flat-panel detector.

Optical lenses are needed to reduce the area of the projected light to fit the CCD array, which subsequently converts the light energy into electrical charges

Lens coupled CCD

One drawback of the lens system is a decrease in the number of photons reaching the CCD, resulting in a lower signal-to-noise ratio (SNR) and relatively low quantum efficiency.

Lens coupled CCD…..

Slot-scan CCD

• Slot-scan CCD systems make use of a special x-ray tube ( tungsten anode) with a collimated fan-shaped beam, which is linked to a simultaneously moving CCD detector array having a matching detector width.

• The combination of a small collimated beam and a concordant detector reduces the impact of scattered radiation in the image, since much of this radiation will escape without detection.

• Relatively low quantum efficiency of slot-scan CCD systems can be offset by the resulting lower image noise.

The exposure time to the patient is about 20 msec, and the readout process takes about 1.3 seconds.

Because of the need for fixed installation, slot scan CCD systems are dedicated to chest radiography, mammography, or dental radiography.

CCD in general

Advantages –

• Relatively cheaper• Individual defective components

can be replaces rather than changing the entire detector

• Upgradeable to future innovations

Limitations –

• Bulky design• Relatively small CCD arrays (2-5 cm)

than the typical projected X-ray areas – hence require demagnification and optical coupling

• Optical system – more signal noise• Thermal noise in CCD can degrade

mage quality• Repeated exposure to X-rays may

damage optical system

Small overall design, which allows integration into existing Bucky tables or thorax stands

Image generation with flat-panel detectors is almost a real-time process, with a time lapse between exposure and image display of less than 10 seconds.

Consequently, these systems are highly productive, and more patients can be examined in the same amount of time than with other radiographic devices.

Indirect Conversion with a Flat-Panel Detector ….why ??

Indirect conversion DR systems are “sandwich” constructions consisting of a scintillator layer, an amorphous silicon photodiode circuitry layer, and a TFT array.

When x-ray photons reach the scintillator, visible light proportional to the incident energy is emitted and then recorded by an array of photodiodes and converted to electrical charges.

These charges are then read out by a TFT array similar to that of direct conversion DR systems.

Indirect Conversion with a Flat-Panel Detector -

Indirect Conversion with a Flat-Panel Detector / TFT

CsI or Gd2O2S

The scintillators (in FPD) usually consist of CsI or Gd2O2S

CsI based FPD - are highly vulnerable to mechanical load because of their fine structure, these systems cannot be used outside of fixed installations and therefore lack mobility.

The advantage of CsI-based scintillators is that the crystals can be shaped into 5–10 micrometer wide needles, which can be arranged perpendicular to the surface of the detector.

This structured array of scintillator needles reduces the diffusion of light within the scintillator layer

As a result, thicker scintillator layers can be used, thereby increasing the strength of the emitted light and leading to better optical properties and higher quantum efficiency

Gd2O2S based FPD - resistant to mechanical stress as are storage phosphors and hence are portable.

Key features of Direct Digital Conversion

X-rays > Electrical signals

No intermediate light production

Detector material – Amorphous Selenium

Maintains high resolution of images as photoconductor thickness is increased

Moderate DQE (effficiency) for conventional radiography but high DQE for mammography KV range

Very sensitive to ambient temperature variations

X-rays > Light > Electrical signals

Used Phosphors – Thallium doped Cesium Iodide (CsI) or Gadolinium Oxy-Sulphide (GdO2S)

More light scatter, so less spatial resolution

Generates poorer resolution images as phosphor thickness is increased

High DQE (Efficiency) for Conventional range KV range

Less sensitive to ambient temperature changes

Key features of Indirect Digital Conversion

1. Image Acquisition2. Image Processing3. Image Display / viewing / post-

processing4. Image Storage

For an image on a screen to have the quality approaching that of a film image, a special monitor must be used with a resolution of 1024 x 1024 pixels

Viewing

After exposure and readout, the raw imaging data must be processed for display on the computer.

Greatly influences the way the image appears to the radiologist .

AIM - to improve image quality by reducing noise, removing technical artifacts, and optimizing contrast for viewing.

Spatial resolution (the capacity to define the extent or shape of features within an image sharply and clearly) cannot be influenced by the processing software because it is dependent on the technical variables of the detector (eg, pixel size).

Image Post- Processing

Contrast adjustments

Contrast enhancement - makes anatomic structures more visible and distinguishable

Contrast reduction - results in smoothing of the structures

Edge Enhancement

Provides sharper delineation of the fine structures of bones.

Black and White Reversal

1. Initially acquired raw data without any processing2. Contrast enhancement makes anatomic structures more visible and distinguishable3. Contrast reduction results in smoothing of the structures4. Edge enhancement provides sharper delineation of the fine structures of bones

Positioning MarkersAdd predetermined text or free textZoom and roam imageInvert imageShow/hide histogram (exposure details)Advanced measurement options

(Orthopedic Application)Stitching for full leg/full spine

Image Post- Processing…….

Image Post- Processing…….

Caution - If one feature is being improved, others may be suppressed, so that unintended and unwanted masking of diagnostically relevant features may occur.

Consequently, image processing must be optimized carefully for each digital radiography system.

Image processing software is usually bundled with the detector and cannot be replaced by other software (in DDR).

Aspects of Image Quality

Pixel Size, Matrix, and Detector SizeSpatial ResolutionModulation Transfer FunctionDynamic RangeRadiation Exposure

Aspects of Image Quality

Pixel Size, Matrix, and Detector Size:

Digital images consist of picture elements, or pixels. The two-dimensional collection of pixels in the image is called the matrix, which is usually expressed as length (in pixels) by width (in pixels)

Maximum achievable spatial resolution is defined by pixel size and spacing. The smaller the pixel size (or the larger the matrix), the higher the maximum achievable spatial resolution.

The overall detector size determines if the detector is suitable for all clinical applications. Larger detector areas are needed for chest imaging than for imaging of the extremities

Spatial Resolution:

Definition - Spatial resolution refers to the minimum resolvable separation between high-contrast objects.

In digital detectors, spatial resolution is defined and limited by the minimum pixel size.

Increasing the radiation applied to the detector will not improve the maximum spatial resolution.

On the other hand, scatter of x-ray quanta and light photons within the detector influences spatial resolution.

Therefore, the intrinsic spatial resolution for selenium- based direct conversion detectors is higher than that for indirect conversion detectors.

The older generations of storage phosphors did not have diagnostically sufficient intrinsic spatial resolution

For digital mammography, the demanded diagnostic spatial resolution is substantially higher indicating the need for specially designed dedicated detectors with smaller pixel sizes and higher resolutions

Modulation Transfer Function:

Definition - capacity of the detector to transfer the modulation of the input signal at a given spatial frequency to its output .

At radiography, objects having different sizes and opacity are displayed with different gray-scale values in an image.

MTF has to do with the display of contrast and object size. More specifically, MTF is responsible for converting contrast values of different-sized objects (object contrast) into contrast intensity levels in the image (image contrast).

MTF is a useful measure of true or effective resolution, since it accounts for the amount of blur and contrast over a range of spatial frequencies.

Dynamic Range

Dynamic range is a measure of the signal response of a detector that is exposed to x-rays .

In conventional screen-film combinations, the dynamic range gradation curve is S shaped within a narrow exposure range for optimal film blackening .

Thus, the film has a low tolerance for an exposure that is higher or lower than required, resulting in failed exposures or insufficient image quality.

For digital detectors, dynamic range is the range of x-ray exposure over which a meaningful image can be obtained. Digital detectors have a wider and linear dynamic range, which, in clinical practice, virtually eliminates the risk of a failed exposure.

Dynamic Range Curve

Detective Quantum Efficiency (DQE):

Deficiency - Efficiency of a detector in converting incident x-ray energy into an image signal.

Calculated by comparing the signal-to-noise ratio (SNR) at the detector output with that at the detector input as a function of spatial frequency .

Dependent on radiation exposure, spatial frequency, MTF, and detector material.

High DQE values indicate that less radiation is needed to achieve identical image quality; increasing the DQE and leaving radiation exposure constant will improve image quality.

The ideal detector - DQE of 1, meaning that all the radiation energy is absorbed and converted into image information.

In practice, the DQE of digital detectors is limited to about 0.45 at 0.5 cycles/mm.

DQE chart

Radiation Exposure:

The higher DQE values of most digital detectors compared with screen-film combinations suggest that, besides providing better image quality, digital detectors have the potential for substantially lowering patient exposure without a loss of image quality.

The most obvious way to minimize patient exposure is to greatly reduce the number of failed exposures and requisite additional images.

This reduction is made possible by the wider dynamic range of digital detectors compared with conventional screen-film combinations.

Unlike storage-phosphor systems, in which the possibility of exposure reduction is limited, DR systems offer a significantly higher potential for general exposure reduction because of their far superior quantum efficiency.

Several studies have shown that a considerably lower exposure is required for equivalent depiction of anatomic details with flat-panel detectors than with storage phosphor systems and screen-film combinations.

In summary, reduction of exposure in flat-panel detector digital radiography is possible, to some extent regardless of the clinical situation.

1. Image Acquisition2. Image Processing3. Image Viewing / Display / Post

processing4. Image Printing / Storage / Archival

Laser Printers

NIMS – Fujifilm Dry Pix 7000

A Picture Archiving and Communication System is an inter and intra-institutional computation system that manages - data acquisition , transfer, storage, distribution display and interpretation of medical images,

all integrated with various digital networks .

PACS

Why PACS ?

Radiologists need to view, archive, and retrieve patients' images.

they also need to retrieve and recall complex and rare pathologic, anatomic, and radiologic knowledge and compile, retrieve, and consult medical records and reports.

Finally, they have to be able to communicate results to referring physicians and colleagues.

Components of PACS

Digital acquisition devicesNetworkDatabase serverArchival systemRadiology information system / Hospital

Information System (RIS / HIS)Soft copy displayEarly remote access (for the referring

clinician)

Short term-rapid access Long term-slow access Duplicate-off site for disaster

recovery

• Scheduling, • Demographics, • Patient information, and • Billing database components• Reports

PACS - overview

HIS

Once correctly installed, no information is lost and available when needed

Comparison with previous examinations available at all times

Simultaneous viewing in different placesRetrieval easyPost processing manipulationsFilm budget reducedTele-radiology

Advantages of PACS

Technically complex ,Dedicated maintenance program requiredTraining requiredNo fall back after installation Failure of individual workstations or

acquisition components will affect functions and data flow in the local PACS branch, failure of the PACS controller or main PACS archive server can cripple the entire PACS operation.

Disadvantages of PACS

Artifacts in Digital Radiology (CR+DR)

Image overlap from different exposures

Image Compositing

The rapid acquisition of images can result in latent signal from one exposure lingering into the readout of subsequent exposures, producing what appears to be an incomplete erasure of the previous image, known as Image lag / Ghosting.

Mainly a DR artifact because of rapid image acquisition ability

Image lag / Ghosting

Flawed Gain CalibrationDetector LagBackscatter (in portable DR due to thin

backside shielding – to make it lighter)

Innovations and Recent Advances

(a) Tomosynthesis:

Multiple low dose exposures are given from various angles while the X-ray tube moves in an arc and the detector remains stationary.

Multiple images with different focal zones are possible to be created by addition of these low dose images after pixel shift. It emphasizes contrast in a particular layer of a region of body.

Generated images can be viewed singly or as a cine loop.

It is considered useful in Chest, IVU studies and mammography

(b) Dual-energy imaging:

By using a high and low kilo-voltage technique, two datasets are created. Soft tissues and bones can be separately depicted by this method.

Dual-energy techniques are most effective when both images are acquired simultaneously. Similar results are obtained with two exposures within a very short period of time.

This is useful in chest radiography, particularly for the evaluation of partially calcified nodules and pleural plaques.

(C) Computer aided diagnosis (CAD) software programs:

These are important in early detection of cancer of the lung and breast. The suspicious areas are marked by the software for review by the radiologist.

The efficiency of CAD software program is related to its sensitivity and specificity profile.

The main advantage of CAD is that it permits a radiologist to avoid overlooking diagnostically significant findings.

(d) Automatic image stitching:

Useful in determining precise measurements in lengthy anatomical regions like the spine or lower limbs.

The largest flat-panel DR plates available today are 43 × 43 cm. Using these detectors, only a limited portion of the body part can be imaged at one given time, thus making these detectors inadequate for studying the whole spine or the entire lower limb.

To overcome this problem, multiple sequential exposures at different patient positions are acquired in a still patient. Automatic stitching is then performed to reconstruct a larger composite image. This special software enables pixel shift and overlap.

(e) Mobile DR:

This is in general a 17 × 14-inches flat panel detector (FPD) connected by a cable to a mobile x-ray system having a monitor.

The use of mobile DR systems is hampered by the fragility of the FPDs and the high costs. A mobile DR system, when compared with an FSR system, avoids problems related to the availability, storage, transportation and disposal of films and chemicals.

(f) Wireless FPDs:

Wirelessly transfers image data to the DR system (Pixium 3543, Thales)

It has no cables and does not interfere with surrounding machines.

Typically a 17 x 14-inch image is made available within 3 sec. This allows radiography of difficult regions of the body like the axilla or the TM joint and enables radiography in unusual positions as in a flexed knee, or in a limb with limited mobility due to contractures.

Innovations and Recent Advances

Some of the drawbacks of CR systems, namely cassette handling, long read out time of PSP plates, low DQE and poor resolution

Have been addressed by newer innovations and technological advances.

(A) Automated CR systems with fast readout:

Automated CR systems reduce the readout time less than 10sec

In these systems there is no cassette handling, leading to totally automatic image data acquisition

(B) Newer phosphors for PSP plates:

Commercially available PSP plates have unstructured phosphor like rubidium chloride or barium fluorohalides doped with Europium.

A needle-shaped phosphor cesium bromide, has been newly introduced, for example, in Konica Minolta's Regius 370 Upright DR, and is considered more efficient due its structured configuration of crystals.

It reduces light diffusion because of the needle shaped configuration that acts as light guide. In addition the newer phosphors are more efficient with an increased DQE.

(C) Mobile CR systems:

Mobile X-ray unit with an integrated CR reader.

They are easy to use and offer quick image availability in less than 25 sec.

Comparative analysis & overview

Relatively cheaper (c/w DR)Can be incorporated into existing

radiography systemCassettes and imaging plate relatively more

sturdy (c/w DR)

CR - Advantages

CR - DisadvantagesRelatively more time for image processing

(c/w DR)Less DQE (c/w DR)

Increased workflowIntegrated high power X-ray system of 30-100

KW – very short exposure times – eliminating motion blur

Reduction in radiation dose possible as per ALARA principle

Presets available for various anatomical studies

Automatic Exposure Control (AEC) facilityAutomatic filter, focal spot size and tracking

for easy positioning

Digital Radiography (DDR) - Advantages

High initial cost

Some radiographic views are difficult to obtain as detectors are generally not free to be placed in any position

Fragile detectors – careful handling

DR - Disadvantages

Radiation Exposure

ENTRANCE SURFACE DOSE

STANDARD RADIOGRAPHIC EXAM USING SFR,CR,DDR

G compagnona, Balani et al: BJR NOV 2006

SFR – Screen Film RadiographyCR – Computed RadiographyDDR – Direct Digital Radiography

Moving From Analog to Digital – Revenue ?

NIMS FIGURES AT A GLANCE

SEPT 2009-AUG 201O - CONVENTIONALSEPT 2010-AUG 2011 - DIGITAL

Analog (conventional)

CR DR

Installation Cost + ++ ++++

Radiation reduction not possible possible Definite reduction possible

Fragility - + +++

Spatial resolution + + ++ (high quality monitors)

DQE + +++ ++++

Dynamic range + (‘S’ shaped curve)

+++ (Linear & wide)

+++ (Linear & wide)

Post processing Not possible possible possible

PACS and teleradiology

Not possible possible possible

Image display time +++++ ++ (upto 25 sec)

+ (< 10 sec)

Overview

Conventional Radiography is evidently the last of the radiology modalities to embrace and incorporate digital technology.

The future of radiography will be digital.

CR is a simple and cost effective technology that permits use of existing radiographic equipment. It has been suggested that for moderate workload (upto 70-90 films per day), a CR system is adequate.

High cost of a DR system is justified only when the workload is

much beyond this level.

Lastly, a change over to digital technology is essential to create a fully digital 'filmless' radiology department and fully reap the benefits of implementing RIS and PACS programs.

CONCLUSION

Advances in Digital Radiography: Physical Principles and System Overview - May 2007 RadioGraphics, 27, 675-686.

Artifacts in Digital Radiography - AJR January 2012 vol. 198 no. 1 156-161.

Christensen’s : physics of diagnostic radiology.

Internet.

References -

cr, dr and recent advances

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